Control system for circulating fluids



Dec. 27, 1938. CUNNINGHAM 2,141,206

CONTROL SYSTEM FOR CIRCULATING FLUIDS Filed Nov. 18, 19:53 2 Sheets-Sheet 1 LEWIS L. CUNNINGHAM Dec. 2 7, 1938. 1 L; CUNNINGHAM 7 2,141,206

' I CONTROL SYSTEM FOR CIRCULATING FLUIDS Filed Nov. 18, 1953 2 Sheets-Sheet 2 will u-zwss L. CUNNINGHAM.

Patented Dec. 27, 1933 UNITED STATES PATENT OFFlCE CONTROL SYSTEM Fon cmoom'rme FLUIDS Lewis L. Cunningham, Minneapolis, Minn, as-

signor to Minneapolis-Honeywell Regulator Company, Minneapolis Delaware Minn, a corporationof Application November 18, 1933, Serial No. 698,039

7 Claims.

The present invention relates to the control of circulating fluids such, forexample, as are employed in the control of temperature.

One of the objects of the present invention is 6 the provision of a system-for controlling the flow of a temperature changing fluid to a temperature changing device,'the control system being so arranged that the fiuid is permitted to flow to the stantial'ly equal duration and varying the intervals between the termination of one cycle and the initiation of the next succeeding cycle in accordance with some temperature condition, such as changes in the outdoor temperature. In

such a system, the unchanging periods of steam flow are predetermined so that each cycle of I steam flow is only long enough to completely fill all of the radiators in the system and the steam fiow, is thereafter stopped so that each of the 39 radiators has a stored heat capacity corresponding to itssize. The maximum length of time that the intervals between steam feeding-periods may persist is limited, particularly in the control of hotels, etc. so that no oneof the ra- 35 diators can become cold and give the guests the impression that the roomsare underheated. This provision also constitutes an object of the invention.

Another of the broader objects of the inven-' 40 tion is the provision of a system for controlling the flow of fluids wherein there is a variable demand, the system being so arranged that an'initial maximum demand can never be made. For

instance, in a heating system wherein a boiler the actual supplying o1 fluid thereto. Specifically, upon a demand for. steam, a plurality of valves are sequentially opened with an appreciable delay between the successive opening'of the various valves so that the demand is gradually increased instead of starting out at the maximum..

A further object of the invention is the provision of a temperature changing systemfor a large building in which the building is divided into two or more zones depending upon variable demands on the various zones by reason of their being subjected to varying wind directions, wind velocities and solar radiation, and providing separate temperature changing devicesand separate controls for each zone. Preferably, each of the various zone controls includes a thermostat which is affected by the outdoor temperature conditions to which the particular zone is subjected.

Another object of the invention is the provision of a temperature control system for a plurality of spaces in which the temperature changing means is controlled both by the average temperature in two or more of the spaces and by the outdoor temperature.

Other objects of the invention lie in the combination of the various above-mentioned systems to form various complete systems of temperature control and also include the various combinations and subcombinations of elements and their inter-relation.

Further objects of the invention will be evident from the following detailed description, accompanying drawings and appended claims.

For a more complete understanding of the invention, reference may be had to the following description and accompanying drawings, in which,

Fig. 1 is a schematic showing of the complete system of the present invention as applied to the heating of a large building, and

Fig. 2 is adiagrammatic showing of the control apparatus and circuits by which certain parts of the system of Fig. 1 are controlled.

Referring first to Fig. 1 of the drawings, a large building which it is desired to heat is generally indicated at 10. The building includes a basement II which contains a large steam boiler l2. The steam boiler I2 is heated by an oil burner l3 which in turn is controlled'by a steam pressure responsive switching mechanism that dominates the operation of the usual control box I 5' through control wires l6. Power is supplied to the control box IE. through supply line l1.

The pressure responsive switching mechanism I4 the average temperature of all of the rooms.

operates normally to maintain a constant steam pressure in the boiler l2.

' Steam from the boiler l2 first passes through a diaphragm type pressure regulator |8 of wellknown construction, then traverses an electrically operated valve I9 and passes through mains and 2 I. The electrically operated valve I9 is controlled by a pressure responsive potentiometer 22 through a reversible motor mechanism 23. The reversible motor mechanism 23 and the electrically operated valve I9 preferably take the general form of mechanism shown in applicants copending application Ser. No. 535,886 filed May 8th, 1931 which issued February 5, 1935, as Patent No. 1,989,972. I

The function of pressure regulator l8 is to deliver steam from the boiler l2 to mains 2D and 2| at a constant reduced pressure. If there should be a sudden demand on the boiler l2 for steam, it has been found that the diaphragm pressure regulator l8 will tend to gulp and hunt before it finally settles down to deliver a steady reduced pressure to mains 29 and 2|, and for this reason, the electrically operable valve I9, which responds to variations in steam pressure on the eduction side of the pressure regulator l8, has been included whereby the valve I9 is slowly opened and closed upon changes in such pressure to steady the action of the pressure regulator l8.

The mains 20 and 2| extend upwardly through the entire building l8 and terminate in the attic 24. A first riser 25 is connected to main 2| through an electrically controlled valve 26. This riser 25 extends downwardly through the building and supplies steam to radiators 21 located in rooms 28. A similar riser 29 is connected to main 2| through an electrically controlled valve 38 and supplies steam to radiators 3| located in rooms 32. The groups of rooms 28 and 32 are herein shown as comprising one of the several zones of the building l8, there being in actual practice a separate zone for each part of the building that is affected differently by outside weather conditions. This zone has been shown as comprising two groups of rooms which are supplied with steam from a single main through two risers. In actual practice, depending upon the size of the building and the number of rooms contained in each zone, there may very well be a larger number of risers per zone and the two risers shown herein are to be understood as merely illustrative of one embodiment of the invention. The electrically controlled valves 26 and are controlled by a thermostatic device 33 which includes a bimetallic thermostatic actuating element 34 which responds to weather conditions outside of the building I6. Each of the rooms 28 and 32 is provided with a vent 35 and all these vents 35 are connected to a suction fan 36 by means of pipes 31. The'fan 36 operates to withdraw air from each and every one of the rooms 28 and 32 and discharges this air to the outdoor atmosphere. A thermostatic device 38 responds to the temperature of the air withdrawn from all of these rooms and in this manner responds to The vents 35 and piping 31 may be especially installed for this purpose or, in some cases, it will be possible to place the thermostat 38 so as to respond to air withdrawn from the various rooms for ventilating ducts which are already existent in the building.

The main 20 similarly supplies two risers 40 and 4| through electrically controlled valves 42 and 43. The riser 40 supplies steam to radiators 44 located in rooms 45, whereas the riser 4| supplies steam to radiators 46 located in rooms 41. Each of the rooms and 41 is provided with a vent 48 and all of these vents are connected to suction fan 36 through piping 49. A thermostatic device 58 responds to the temperature of the air withdrawn from the rooms 45 and 41 and a thermostatic device 5| which includes helical bimetallic thermostatic element 52 is exposed to outside weather conditions and controls the operation of valves 42 and 43. These rooms, radiators, vents, etc. comprise a second zone similar in every manner to the first zone except that the second zone is exposed to different weather conditions and the heating demand thereof therefore differs from the demand of the first zone.

The manner in which thermostatic devices 33 and 38 control valves 26 and 30 is exactly the same as the manner in which thermostatic devices 58 and 5| control the valves 42 and 43 and, in the following detailed description, the com plete control mechanism for only a single zone will be described but it is to be understood that each and every other zone is supplied with a similar control mechanism.

Valve 26 is adapted to be controlled either manually or automatically by suitable switching mechanism. The manual switching mechanism comprises a flexible blade 55 which is normally in engagement with a contact arm 56 and a second flexible blade 51 which is normally in engagement with a contact arm 58. A manual operator 59 is provided with a finger 68 which, upon proper manuipulation, will engage flexible blade 55 to move it out of engagement with contact arm 56 and into engagement with a contact arm 6| or will engage flexible blade 51 to move it out of engagement with contact arm 58 and into engagement with a contact arm 62. Contact arm 56 and flexible blade 51 are electrically connected. The automatic switching mechanism comprises a flexible blade 63 which is normally biased into engagement with a contact 64 but is adapted to be flexed into engagement with a contact 65.

With the parts in the position shown, the manual operator 59 is in automatic position and flexible blade 63 is engaged with contact 64 so that a closing circuit for valve 26 is completed. This closing circuit is as follows: line 66, flexible blade 55, contact arm 56, flexible blade 51, contact arm 58, wire 61, flexible blade 63, contact 64, wire 68, Wire 69 and valve 26 to line 12. When flexible blade 63 is flexed into engagement with contact 65, a valve opening circuit is completed for valve 26 as follows: line 66, flexible blade 55, contact arm 56, flexible blade 51, contact arm 58, wire 61, flexible blade 63, contact 65, Wire 16, wire 11, and valve 26 to line 12. If it should be desired to manually open valve 26, manual operator 59 is manipulated so that finger engages flexible blade 55 to move it from engagement with contact arm 56 and into engagement with contact arm 6| to complete a valve opening circuit for valve 26 as follows: line 66, flexible blade 55, contact arm 6|, wire 8|, wire 11, and valve 26 to line 12. Similarly, if it be desired to manually close valve 26, manual operator 59 is manipulated to bring finger 60 into-engagement with flexible blade 51 to move the latter from engagement with contact arm 58 and into engagement with contact arm 62. A closing circuit for valve 26 is thereby established as follows: line 66, flexible rod 93 which is adapted to engage a switch arm tact arm 62, wire 82, wire line 12.

If desired, indicating lamps can be suitably associated with the valve 26, in any of the wellknown manners, to indicate whether the valve is open or closed.

The valve 30 is controlled by a similar switching mechanism and circuit arrangement, the parts of which have been referenced 55A and 82A inclusive tocorrespond with the similar parts and switches for operating valve 26. It will be understood that there could be a larger number of risers and valves in each zone and that there should be one of these switching systems for each and every valve. The automatic switches are controlled by a timer mechanism which'includes a timer motor having a rotor 83 and a field winding 84. The rotor 83 drives a cam shaft 85 through suitable gear reduction indicated generally as 86. The cam shaft 85 carries two relatively adjustable cams 81 and 88 which, upon rotation of cam shaft 85, successively engage the extended ends of'flexible blades 63A and 63 to flex them into engagement with their contacts 65A and 65 and, upon continued rotation of cam shaft 85, the flexible blades 63A and 83 will ride off the end of cam 81 and move back into engagement with contacts 64A and 64. The flexible blades 63A and 63 are spaced about cam shaft 85' so'that they are successively or sequentially operated by cams 81 and 88 for a purpose which will hereinafter appear. Cam shaft 85 also carries a stopping switch cam 89 and a maintaining switch cam 90 which are provided with lobes 9I and 92 respectively. Lobe 9I operates a push 69, and valve 26 to 94 and move the same to the position shown in the drawings wherein it is latched by the hooked end 95 of an armature 96 whichis pivoted at 91. Arinatu. c 35 is adapted to be attracted by an electromagnetic coil 98 and is biased away from electromagnetic coil 98 by a spring 99. Switch arm 94, when released by latch 95, is adapted to engage a switch arm I00. Lobe 92 operates a push rod IOI which engages a switch arm I02 and moves the same out of engagement with a switch'arm I03.

Upon momentary energization of electromagnetic coil 98, armature 96 is attracted and the latch 95 thereof releases switch arm 94 for movement into engagement with switch arm I00. Field coil 84 of the timer motor is thereupon energized by a circuit as follows: line I05, wire I06, wire I01, switch arm 94, switch arm I00, wire I08, field winding84, wire I09 and wire IIO to line III. Energization of field winding 84 causes rotation of cam shaft 85in a counter-clockwise 1 direction as viewed from the left in Fig. 2. Initial rotation of cam shaft 85 in this direction moves lobe 92 from under push rod IN and allows this push rod to move downwardly whereupon switch arm I02 moves into engagement with switch arm I03 and establishes a maintaining circuit for field winding 84 which is independent of switch arms 94 and I00. This maintaining circuit is as follows: line I95, wire I06, wire I01, wire II2, switch arm I02, switch arm I03, wire II3, wire I08, field winding 84, wire I09 and wire IIO to line I I I. Shortly thereafter cam 88 engages flexible blade 63A and moves the same into engagement with contact 65A to open valve 30 whereupon steam traverses riser 29 and flows to the various radiators 3I. Continued rotation of cam shaft 85 thereafter causes cam 88 to engage flexible blade 63 and move the same into engagement with contact 65 whereupon valve 26 is opened and steam flows through riser 25 and to the various radiators 21. The valves 30 and 26 remain open until cam 81 rotates from under flexible blades 63A and 63 respectively whereupon these blades return to the position shown in Fig. 2 and cause their respective valves 30 and 26 to close. In this manner, all of the valves in a single zone are opened with a time interval between .the successive opening of any two valves so that the full demand, of a single Zone is never initially placed on the boiler. In other words, the demand of a single zone for steam from the boiler I2 is gradually built up instead of instantly increasing from a. zero demand to full demand. During the a full revolution, the lobe 92 raises push rod IOI which, in turn raises switch arm I02 from engagement with switch arm I 03. Field winding 84 is thereby deenergized and the cam shaft has returned to the position shown in the drawings and remains in this position until electromagnetic coil 98 is again momentarily energized.

The. circuit to electromagnetic coil 98 is c ontrolled by a switch which comprises a stationary switch arm. I I5 and a movable switch arm IIS. This energizing circuit is as follows: line I05, wire I06, wire II1, switch arms II5 and H6, wire II8, electromagnetic coil 98, wire H9 and wire H to line III. Switch arm II 6 is normally, biased from engagement with switch arm I but is intermittently moved into engagement with switch arm II5 at frequencies which are varied by mechanism which will now be described.

Switch arm II6 extends in back of a ratchet wheel I20 which is pivoted or journalled at I2I. Ratchet wheel I20 carries on its rear face two switch actuating buttons I22 and I 23 which are adapted, upon clockwise rotation of ratchet wheel I20, to engage switch arm II6. to move the same into contact with switch arm II5. Counterclockwise movement of ratchet wheel I20 is prevented by a stop pawl I 24 which is constantly urged into engagement with the teeth of ratchet wheel I20 by a compression spring I25. An actuating pawl I26 is biased into engagement with the teeth-of ratchet wheel I 20 by means of a compression spring I21 and is pivoted to an actuating arm I28 as indicated at I29, the actuating arm I28 being pivoted at the axis of ratchet wheel I20. A tension spring I 30 tends to rotate actuating arm I28 in a counter-clockwise direction.

Actuating arm I28 is provided with a laterally extending pin I3I which enters an elongated slot I32 formed in an actuating link I33. The other end of actuating link I33 is journalled on a crank pin I34 whichis secured to a disc I35 that is rotatable with a gear I36. Gear I36 is driven by a motor rotor I31 through suitable speed reducins, mechanism I38. Rotor I31 is provided with a field winding I39 which is constantly energized during the operation of the control system. A stop link I40, which is pivoted to actuating arm I28 as at I 4|, is provided with a plurality of stop surfaces I42, I43, I44, I45, I46, I41, I48 and I49. The upper end of stop link I40'is pivoted to a connecting link I 50,the other end of which is pivoted at a point directly above the axis of ing arm I28 and actuating link I33.

ratchet wheel I20 and which point is likewise preferably the pivotal point for stop pawl I24.

Actuating arm I28 is slowly reciprocated about pivot I2I by virtue of rotation of disc I35 and its connection thereto by actuating link I33. Each clockwise rotation of actuating arm I28 advances ratchet wheel I20 (9 teeth for example) when the downward movement of stop link I40 is not restricted. However, if the movement of stop link I40 is restricted so that actuating arm I28 cannot move in a counter-clockwise direction the full amount allowed by actuating link I33, then in that event, the slot I32 of actuating link I33 will permit of relative movement between actuat- V In this manner, by allowing stop link I40 to only move downwardly a small distance, the counter-clock wise rotation of actuating arm I28'wi1l be relatively small and the clockwise movement thereof will be equally small so that ratchet wheel I20 is only moved forward a small number of teeth at a time. In this manner, by varying the movement of stop link I40 so that ratchet wheel I20 is moved larger or smaller numbers of teeth for every rotation of disc I35, the time intervals at which buttons I22 and I23 will be operated to move switch arm II6 into engagement with switch arm II5 may be varied.

The amount of movement allowed stop arm I40 is preferably varied automatically as a result of the change in one or more conditions which vary the amount of heating required by any particular zone. In the present embodiment of the invention, there is provided a vertical plate I55 which is connected to a plunger I56 that is positioned by the conjoint action of a pair of solenoid coils I51 and I58. The plate I55 is normally free to stop link I40, the plate I55 is moved downwardly whereby undue strain is not -placed upon plunger Solenoid coils I51 and I58 are connected in series across the secondary I60 of a step down transformer I6I having a high voltage primary I62. The junction of solenoid coils I51 and I58 is connected to a contact finger I63 by means of wires I64, I65 and I66 through a manually adjustable resistance I61. The contact finger I63 is controlled by thermostatic element 34 and sweeps across a resistance I68 upon changes in the outdoor temperature to which thermostatic element 34 responds. One end of resistance I68 is connected to the outer end of solenoid coil I51 through a rheostat I69 by means of wires I10 and HI. I68 is connected to the outer end of solenoid coil I58 through a rheostat I12 by means of wires I13 and I14.

Duct thermostat 38 is herein shown as comprising a thermostatic bellows I15 of well-known construction which moves a contact finger I16 across a resistance I11. Resistance I11 is connected in parallel with resistance I68 by means of wires I18 and I19. Contact finger I16 is connected to contact finger I63 by wires I80, I8I and through a switch I82. Switch I82 is a centrifugal switch controlled by the rotor I83 of the induction fan 36. Associated with rotor I83 is a field winding I84 which is controlled by a time controlled switch I85. Time controlled switch I85 is shown as being controlled by a cam I86 whereby the operation of the blower 36 may be discontinued during predetermined-periods of the day or move back and forth but upon engagement by into engagement with a stationary bracket I59 Similarly, the other end of resistance night if it should be so desired. The circuit for field winding I84 is: line I05, wire I81, time controlled switch I85, field winding I84 and wire I88 to line I I I.

Operation of the complete system With the parts in the position shown in Fig. 2, the outdoor temperature is intermediate as indicated by contact finger I63 being in engagement with the center of resistance I68. Likewise, the average temperature of the various rooms is substantially that desired'as indicated by engagement of contact .finger I16 with the central portion of resistance I11. As a result, solenoid coils I51 and I58 are substantially equally energized so that plunger I56 assumes a central position and stop plate I55 is in such position that it will be engaged by stop I46 of stop link I40 upon the next succeeding downward movement thereof; Stop I46 allows actuating arm I28 to move downwardly sufiiciently that ratchet wheel I20 will be advanced six teeth each time disc I35 makes a complete revolution. The ratchet wheel I20 is provided with 120 teeth and since there are two buttons I22 and I23, the ratchet wheel must be advanced 60 teeth for each closure of switch I I5- II6. With the ratchet wheel I20 being advanced at the rate of six teethper revolution of the disc I35, which revolves at a speed of approximately one revolution for every 100 seconds, the switch I I5-- ,-I I 6 will be closed approximately every 1'7 minutes.

Each time the switch is closed, electromagnetic coil 98 is energized to start cam shaft 85 on one of its cycles of rotation. During this cycle of rotation of cam shaft 85, the valves 30 and 26 are successively opened for periods of about two minutes, it requiring 5 minutes for cam shaft 85 to make a complete revolution.

In this manner, steam is supplied for periods of two minutes each with intervals of approximately 15 minutes between these feeding periods for the particular prevailing outdoor temperature.

If the outside temperature should become very mild so that contact arm I63 moves to the lower end of resistance I68, solenoid coil I51 will be substantially short-circuited whereby the plunger I56 will move to the extreme right and stop plate I55 will be moved into the path of stop I42. Movement of actuating arm I28 will thereupon be greatly restricted so that ratchet wheel I 20 will only advance two teeth per revolution of disc I35 with the result that switch I I5-I I6 will only be operated every 50 minutes. In this manner, the intervals between the two minute feeding periods will be greatly increased but it will be noted that the steam feeding periods are of equal duration and that the variable is the interval between the steam feeding periods whereby a variable period is allowed for condensing of steam in the radiators and its dissipation to the rooms.

If the outside temperature should become extremely cold so that the contact finger I63 engages the upper end of resistance I68, solenoid coil I58 will be substantially short-circuited and the plunger I56 will move to the extreme left to bring stop plate I55 under stop I49. With the stop plate in this position, actuating arm I28 is not restricted whatsoever in its movement with the result that ratchet wheel I20 is advanced 9 teeth for each revolution of disc I 35 with the result that switch II5-II6 is closed approximately every eleven minutes.

In this manner, although the steam feeding. periods are never varied in length, the intervals between-such periods are varied in accordance with the change in outdoor temperatureso that the temperature of the various rooms should remain at the desired point.

The thermostat or controller 38 serves to modify the action of the outdoor thermostat or controller 33 according to variations in the average temperature of the rooms 28 and 32. When the contact finger I16 is contacting the central portion of resistance Ill, the solenoid coils I51 and I58 are equally energized insofar as the controller 38 is concerned so that the respective energizations of the solenoid coils I51 and I58 will be dependent entirely upon the action of controller 33. However, if the average temperature becomes too high, contact finger I16 will move upwardly along resistance Ill and tend to energize solenoid windi.-g I5! more highly than solenoid Winding I58. The reverse action takes place if the average temperature becomes lower than that desired. In this manner, the outdoor controller 33 and the average temperature controller 38 cooperate to control the length of the periods between successive valve openings.

The use of an indoor temperature responsive device, such as average temperature controller 38, is particularly desirable since the outdoor thermostat 33 may be necessarily maintain the indoor temperature at the exact desired value because it responds only to outdoor temperatures and only indirectly controls the indoor temperature. The inclusion of an indoor thermostat operates to offset any appreciable deviation of the indoor temperature from the desired value so that the indoor temperature is maintained closer to the desired point that it might be maintained by the sole action of an outdoor thermostat.

The time switch I85 may be utilized to shut down the fan 36 at night, if desired. Whenever rotation of fan 36 ceases, centrifugal switch I82 opens and disconnects contact finger I16 from the control system whereby average temperatur controller 38 is rendered inoperative.

The rheostats I12, I61 and I69 are preferably controlled by a single manually operable member I90 and serve to introduce a variable amount of resistance in the control circuits for solenoid coils I51 and I58 whereby the position of plunger I56v for any given position of controllers 33 and 38 may be adjusted to properly correlate the control system to the particular steam heating systern and building with which it is used.

From the foregoing description of the system of the present invention, it will be readily seen that the periods of feeding steam are always equal and the length of these periods must be determined for each particular installation so that they are only long enough to allow all of the radiators to become properly filled with steam at which time the feeding periods should terminate. The control action is then obtained by varying the intervals between the steam feeding periods. In the spet'zific embodiment herein described, the control system is so arranged that steam will be fed at least every minutes irrespective of the requirements. Such a feature is particularly desirable in heating hotels and the like wherein it is desired to maintain the radiators warm to the touch even in themildest of weather so that the guests will not obtain the impression that no heat is being furnished. For other types of control, it is highly possible that much longer inter vals between the steam feeding periods would be permissible.

It will also be noted that the present system provides for the opening of a plurality of valves at spaced intervals rather than simultaneously in order that the relatively small supply of steam capable of being carried in the boiler will not be immediately exhausted before the automatic controls. have a chance to begin generating more steam.

While a specific embodiment of the invention has been described, it is to be understood that many modifications could be made herein and that the invention is equally applicable to temperature control systems other than heating systems and that at least some phases thereof are applicable to types of control systems other than temperature control systems. I therefore intend to be limited only in accordance with the scop of the appended claims.

I claim as my invention:

1. In combination, a plurality of spaces the temperature of which it is desired to control, a plurality of temperature changing devices, at least one for each space, a supply of temperature changing fiuidfor said devices, fluid flow controlling means in control of the flow of fluid .to said devices, temperature responsive means responsive to the average temperature of said spaces, temperature responsive means responsive to some other temperature condition, and means controlled by the conjoint action of said temperature responsive means for operating the fluid flow controlling means to permit flow of fluid to said devices for successive periods of equal duration and to prevent such flow for intervals of varying duration.

2. In a heating system, in combination, a plurality of spaces to be heated, a plurality of radiators, at least one for each space, a single valve in control of the flow of fluid to said radiators, means for opening said valve for recurring equal periods and for closing the same for intervals of varying duration, said means including an outdoor temperature responsive thermostat and means'controllecl by the average of the tempera-' tures of all of said spaces. 7

3. In combination, a plurality of spaces the temperature of which it is desired to control, a

plurality of temperature changing devices, at-

least one for each space, a supply of temperature changing fluid for said devices, fluid flow'con-- trolling means in control of the flow of fluid to said devices, temperature responsive means responsive to the average temperature of said 4. In combination, a valve, means including a movable member arranged to initiate opening of the valve and to maintain the same open for a definite time, a constantly driven reciprocating member, a driving connection between the reciprocating member and. movable member, anda thermostat associated with said driving connection for varying the amount of movement transmitted to the movable member for each reciprocation of the reciprocating member whereby to vary the intervals between successive valve openings.

5. In combination, a valve means including a movable member arranged to initiate opening of spaces, means responsive to outdoor conditionsthe valve and to maintain the same open for a deflnite time, a constantly driven reciprocating member, a driving connection between the reciprocating member and movable member and in- 5 eluding a ratchet and pawl, and a thermostat associated with the ratchet and pawl and arranged to vary the number of teeth of the ratchet over which the pawl moves whereby to vary the amount of movement of the movable member for each complete reciprocation of the reciprocating member.

6. In combination, a plurality of spaces the temperature of which it is desired to control, means for changing the temperature of all of said spaces, temperature responsive means responsive to the average temperature of all of said and means controlled by the conjoint action of the temperature responsive means and outdoor 20 condition responsive means for controlling the temperature changing means, and time controlled means operative to render said temperature responsive means inoperative during prechanging fluid for said devices, fluid flow control means in control of the flow of fluid to said devices, temperature responsive means responsive to the average temperature of all of said spaces, temperature responsive means responsive to outdoor temperature, connections by which said temperature responsive means cooperate in operating the fluid flow controlling means to permit and prevent flow of fluid to said devices for varying periods, and time controlled means arranged to render the average temperature control means inoperative to control the fluid flow controlling means during predetermined periods. 20

LEWIS L. CUNNINGHAM. 

